The field of the present invention is well drilling and completion systems.
Well drilling and completion equipment includes tubulars which are variously characterized as casing, tubing and liner. For universal application, they are cylindrical in shape and of a length in compliance with the American Petroleum Institute Standard 5C. The term "casing" is typically applied to tubulars which are larger in diameter and used to support the earth's encroachment when drilling a bore hole for a well. Often casing is cemented to the bore hole to define a sound structural member and to prevent migration of unwanted gases, water or other fluids outwardly of the casing. Casing is typically assembled from 40 foot long tubulars with threaded couplings. Wells can extend for several miles into the earth. As the well increases in depth, the hydraulic pressures to which the casing is subjected to increase. Decreases in casing diameter with increasing depth is common, often to avoid experiencing excessive force from such high pressures. Such decreases typically occur in step function as smaller casing is employed.
"Liner" is typically made up of tubulars in an area of well production. Liner can have portions with slots prefabricated through the wall, end closure elements and the like. Liner is typically smaller in diameter than casing and is typically placed in wells after casing to extend from casing into production zones.
Other tubing may be employed within casing to bring production to the surface and for other communication within wells. This too is placed in wells after casing and has a reduced diameter.
To insure the flow of fluids with or without entrained solids are appropriately directed within wells, packers or annular seals are frequently employed to span gaps at radial steps in tubular construction within wells. Packers are also employed to insure the blockage of pressure from unwanted areas.
Additionally, structural support from above frequently is needed for such placements. The compression of tubular strings through placement on the bottom is often considered to be detrimental to the pressure integrity of the structure. Consequently, suspending liner or casing in tension is preferred. Hangers typically are used which employ wedges or other structural devices to grip the inner tubular. Combinations of packers and hangers are also used.